Electric cables which are capable of operating during a fire are more and more required in order to limit fire propagation in buildings Government regulations in various countries now specify that essential electrical circuits be protected in order to ensure that the electrical system be capable of operating to ensure the safety of persons inside the building and also to permit the firemen to be more efficient in controlling and extinguishing fires.
In certain locations, such as high buildings, a minimum amount of time is needed so that all persons may be reached. Therefore, the electrical system during a fire must be able to be maintained at least during that amount of time.
It has been established that some essential electrical circuits must be able to operate for at least two hours or in other case four hours in order to ensure the safety of people. Such systems include, for example, alarms which are, in turn, essential in order to enable other systems to be operated, such as telephone systems, lighting systems, elevator systems, ventilation systems, fire pumps, etc.
Many cables which are presently in use, are capable of resisting temperatures in the neighborhood of 1000.degree. C. However, their resistance is limited to a period of 30 minutes. One cable which is presently used and known under the trademark Pyrotenax, is formed of a copper tube with a silica powder capable of resisting to higher temperatures. However, the rigid copper tube prevents the cable from being easily flexed thereby rendering it difficult to install in various sharp bends or corners, or the like.